[WebAssembly] Update latest implemented SIMD instructions

Summary:
Move instructions that have recently been implemented in V8 from the
`unimplemented-simd128` target feature to the `simd128` target
feature. The updated instructions match the update at
https://github.com/WebAssembly/simd/pull/223.

Reviewers: aheejin

Subscribers: dschuff, sbc100, jgravelle-google, hiraditya, sunfish, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D79973